1. Spacecraft Thermal System
Charles Baker
Code 545
August 16-17, 2005

2. Level 1 - LRO Requirements ESMD-RLEP-0010
Lunar Reconnaissance Orbiter (LRO) Thermal Level System Requirements Traceability
Level 1 - LRO Requirements ESMD-RLEP-0010
Level 2 - LRO Mission Requirements Document RQMT
LRO Technical Resource Allocations 431-SPEC
LRO Electrical Systems Specification 431-SPEC
LRO Thermal Systems Specification 431-SPEC
LRO Mission Concept of Operations 431-OPS
LRO Pointing and Alignment Specification 431-SPEC
Level 3 - LRO Thermal Math Model Specification 431-SPEC
LROC Thermal Interface Control Document 431-ICD
LAMP Thermal Interface Control Document 431-ICD
Diviner Thermal Interface Control Document 431-ICD
LOLA Thermal Interface Control Document 431-ICD
CRaTER Thermal Interface Control Document 431-ICD
LEND Thermal Interface Control Document 431-ICD
Mini-RF Thermal Interface Control Document 431-ICD

3. Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements
Level 2 Req.
Level 3: Requirements
Concept/Compliance
Paragraph
Requirement
MRD-78
Thermal Operational Ranges
431-SPEC , Section 2.3
LRO’s Thermal Control System shall be designed, analyzed, and tested to demonstrate that operational temperature Interface requirements are met during the mission life.
Convert mechanical design into a thermal design. Apply conservative assumptions to bounding operational cases per 431-SPEC Test worst cases in the T-Vac chamber simulating the lunar environment per 431-SPEC Thermal Cycle Qualification to show lifetime in accordance with GEVS.
MRD-79
Thermal Survival Ranges
LRO’s Thermal Control System shall be designed, analyzed, and tested to demonstrate that survival temperature Interface requirements are met during the mission life.
Develop thermal models from mechanical design. Apply conservative assumptions to bounding survival cases per 431-SPEC Test worst cases in the T-Vac chamber. Thermally demonstrate survival in accordance with GEVS.
MRD-31 Power Allocations
431-SPEC , Section 3.2
LRO Thermal’s Heater circuits shall not exceed the allocations shown in Power Allocations Document 431-RQMT
Individually predict heater power required for each heater location and sum the power consumed by each circuit in 431-SPEC
MRD-4 Launch Window
MRD-50 Mission Phases
MRD-52 Sun Avoidance
MRD-100 Thermal Off-Nominal Ops
431-OPS
LRO Thermal shall be designed, analyzed, and tested per bounding thermal cases outlined in LRO Mission Operations Concept Document 431-OPS which will be broken into thermal assumptions in 431-SPEC
The thermal design shall keep all temperatures in limits and not exceed heater power allocation in all attitudes that LRO is baselined to fly in.

4. Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements
Level 2 Req.
Level 3: Requirements
Concept/Compliance
Paragraph
Requirement
MRD-21
Mission Duration
431-SPEC , Section 5.2, 5.4
LRO’s Thermal Control System shall meet performance requirements for the full 14 month duration of the mission.
Conservatively degrade thermal coatings to reflect environment driven degradations. Only use thermal component parts that are compliant with the mission lifetime.
MRD-19 Lunar Eclipses
MRD-20 Spacecraft Safing
431-SPEC , Section 5.4
LRO thermal system shall be designed to maintain all components within the appropriate temperature limits during the lunar eclipse and during spacecraft safing. LRO thermal system will not exceed the lunar eclipse and safing heater power allocation.
Operational and survival heaters will be sized by analysis and proved in test as having sufficient heater power at minimum voltages with GEVS margin to maintain all components within their appropriate temperature ranges during the lunar eclipse and safing periods.
MRD-28 Vehicle Interfaces
LRO thermal design shall be capable of maintaining all components within the appropriate temperature limits from Launch thru Separation including soak back from the third stage.
Pre-separation thermal analysis shall be conducted. Of particular concern is the soak back from the third stage solid rocket motor
MRD-6 Thermal Environments
431-SPEC , Section 5.1
All thermal control systems (TCSs) shall be designed with conservative assumptions about the lunar environment biased hot and cold as outlined in 431-SPEC
431-SPEC defines the Solar Constant, lunar infared radiation, Lunar albedo per orbit location and Beta angle. TSS will be used to predict imposed environmental fluxes.

5. Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements
Level 2 Req.
Level 3: Requirements
Concept/Compliance
Paragraph
Requirement
MRD-70 Structural Stability
431-SPEC
431-SPEC , Section 2.4, 2.5
The LRO thermal system shall predict temperatures on the spacecraft structure. The thermal predicts will be mapped onto the mechanical FEM model for subsequent use in STOP analyses. The thermal induced distortions shall be mechanically/thermally designed to stay within the mission pointing budgets. Spatial and temporal thermal gradients requirements shall be captured in 431-SPEC and verified thru analysis and test.
Perform a STOP analysis. Evaluate thermal gradients thru TSS/SINDA models, modify the thermal/mechanical design to meet the requirements
MRD-81 Monitoring
431-SPEC , Section 2.7
The LRO thermal system shall identify locations for S/C monitored temperature sensors at thermal interfaces. Components and Instruments shall identify locations for S/C monitored temperature sensors within components. Allocations of temperature sensors shall be provided in 431-SPEC
Baseline is to provide two (2) temperature sensors per instrument/component.

6. Lunar Reconnaissance Orbiter (LRO) Temperature Requirements
SUBSYSTEM
COMPONENT
TEMPERATURE RANGE (°C)
Operational
Survival
Mechanical
Structure Propulsion Module
+70 to -50
+80 to -60
Structure -Avionics Module
+50 to -50
+60 to -60
Structure -Avionics to Propulsion
Structure. Instrument Module
Fasteners
+90 to -65
Mechanisms
High Gain Antenna (HGA) Gimbals
-10 to +50
-20 to +60
HGA Boom
HGA Release and Deploy
Solar Array (S/A) Gimbals
S/A Boom
S/A Release and Deploy
Power
Power Subsystem Electronics (PSE)
-10 to 40
-20 to 50
Battery
10 to 30
0 to 40
S/A Cells/Cover Glass
+130 (operating), +140 (non-operating) to
+140 to -175
S/A Substrate

7. Lunar Reconnaissance Orbiter (LRO) Temperature Requirements
SUBSYSTEM
COMPONENT
TEMPERATURE RANGE (°C)
Operational
Survival
Attitude Control System (ACS)
Star Trackers
-30 to +50
-30 to +60
Inertial Measurement Unit
-30 to +65
-30 to +75
Reaction Wheels
-10 to +50
Coarse Sun Sensors
-120 to +80
-130 to +90
Propulsion and Deployables Electronics (PDE)
Box and MTG Hardware
-10 to +40
-20 to +50
Propulsion (Dry Mass)
Hydrazine Tank 1
+10 to 40
N/A
Pressure Tanks (Comment)
+0 to 50
90N Thrusters
22N Thrusters
High Press Transducers
Low Press Transducer
Gas Latch Valve
Liquid Latch Valve
Fill and Drain
Gas System Filters
Liquid Filters
Pressure Regulators
Plumbing Lines
NC Pyro Valves, Pressurant

8. Lunar Reconnaissance Orbiter (LRO) Temperature Requirements
SUBSYSTEM
COMPONENT
TEMPERATURE RANGE (°C)
Operational
Survival
C&DH
Box and Mounting Hardware
-10 to 40
-20 to 50
S Comm
-10 to +40
TT&C Omni Antenna
-120 to +80
-130 to +90
Ka Comm
Ka Baseband Modulator
-10 to +50
-20 to 60
Ka TWTA w/EPC
HGA
+145 to -140
Cosmic Ray Telescope of the Effects of Radiation (CRaTER)
S/C at I/F to CRaTER
-30 to +35
-40 to +50
Diviner
S/C at I/F to Diviner Instr
-50 to +50
-60 to +60
S/C at I/F to remote electronics box
-20 to +50
-70 to +80
Lyman-Alpha Mapping Project (LAMP)
S/C at I/F to LAMP
Lunar Exploration Neutron Detector (LEND)
S/C at I/F to LEND
-30 to +40
Lunar Orbiter Laser Altimeter (LOLA)
S/C at I/F to Optics Assembly
S/C at I/F to Main Electronics Box
Lunar Reconnaissance Orbiter Camera (LROC)
S/C at I/F to NACS
S/C at I/F to WACS
S/C at I/F to SCS
Mini RF
S/C at I/F to Antennae
S/C at I/F to Electronics Package

9. Thermal Block Diagram – Instrument Module
Zenith (Radiator Direction)
LOLA MEB
Star Cams
LROC
IMU
Diviner REB
CRaTER
LEND
LOLA Op Bench
Thermal Isolation
Nadir
Anti-Sun (Radiator Direction)
Instr Optical Bench
Concept: Use zenith facing or anti-sun facing honeycomb panels that are cold biased and use heaters and thermostats to control the temperature

10. Thermal Block Diagram - Avionics
Gimbal Cntrls
Zenith (Radiator Direction)
TWTA
C&DH
PSE
S-Band
Battery
PDE
LAMP
Anti-Sun (Radiator Direction)
Mini-RF Electronics
Nadir
Mini-RF Antennae
Solar Array (shown in Beta 90°)
Diviner
Concept: Use zenith facing or anti-sun facing honeycomb panels that are cold biased and use heaters and thermostats to control the temperature

11. Thermal Block Diagram - Propulsion
Conductive and Radiative Coupling to the Avionics
5# thrusters (8)
RWAs
20# thrusters (2)
Main Tank
Pressurant Tank
Concept: Use RWAs and Avionics module to keep propulsion system warm. Isolate from the third stage and thrusters.

12. Lunar Reconnaissance Orbiter (LRO) Thermal Verification Summary
Analysis
Predict Control Heater Power, Temperatures, Gradients of all thermal I/Fs during all bounding mission modes
Provide inputs to STOP analysis
Design Orbiter Thermal Vacuum test to provide GEVS qualification
Component Tests
All avionics boxes will be thermal cycled (8)
All instruments with be thermal cycled (8) and thermal balanced
Propulsion Module will be thermal cycled (8) and thermal balanced
No thermal components will be component level tested since all thermal components (MLI, T-Stats, Film Heaters, Thermistors are previously space flight qualified)
Orbiter Tests
2 Cold Startups, 2 Hot Startups
Orbiter with be thermal cycled (4) and thermal balanced

13. Lunar Reconnaissance Orbiter (LRO) Thermal Requirements Summary
The thermal group has been working closely with systems to understand and define the mission requirements that drive thermal
Thermal is a back loaded subsystem, but preliminary analyses of the orbiter concept shows the design is feasible
Thermal has established and is carrying sufficient margins to accommodate system changes on the road to CDR - system is robust
Thermal is ready to proceed to PDR